This invention relates to machines for washing the interior of containers and/or filling containers, the containers having spring-loaded closure units. Specifically the invention has been developed for the washing and/or filling of beer kegs. Such a keg has a closure unit which has one or two spring-loaded valve members which act to seal the keg. The closure units are arranged so that the valve members may be opened to fill the keg, or dispense beer from the keg, with the closure unit in place in the keg. Such a keg is filled against a counter pressure of carbon dioxide and beer is dispensed from the keg under a pressure of carbon dioxide.
Washing or filling takes place through a head which engages the neck of the container which in turn contains the closure unit. The head contains a probe which is movable relative to the head to open the valve means of the closure unit against its spring loading. It is not possible to see the action of the probe during washing or filling because the probe is enclosed totally within the head or the neck. If the probe is not fully sealed to the closure unit when washing or filling takes place, malfunctioning will occur. During a washing cycle, washing liquid may not properly enter the keg. During a filling cycle there may be leakage between the beer and the CO.sub.2 which will impair the quality of the beer.
It is an object of the present invention to provide means whereby the position of the probe relative to the head may be reliably sensed.